If you've only ever used Mastodon through an app, you might want to try using it through your server's website too.

Each server has its own website which you can use your account on. To access the web version, just go to your web browser (Firefox, Chrome, Safari etc) on any phone or computer and type the address of your server. Log in with the same ID and password as you do on the app.

For example, if your account is on the server mas.to, you can log in on its website https://mas.to.